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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

16157 results found.

  1. GRB 250912A: VLT observations
  2. GRB 250912A:SVOM/VT optical upper limit
  3. GRB 250912A: LCO optical upper limit
  4. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  5. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 250910B: SVOM/GRM observation
  7. EP250911a: SVOM/VT optical observation
  8. GRB 250911A: MASTER optical counterpart observations
  9. EP250911a: SAO RAS optical observations
  10. EP250911a: Swift-XRT observations
  11. EP250911a: Optical detection with Kinder observations
  12. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  13. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  14. EP250911a: COLIBRÍ optical observations
  15. EP250911a: LCO optical counterpart discovery
  16. GRB 250911A: COLIBRÍ optical counterpart candidate
  17. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  18. GRB 250910A: SVOM/VT optical upper limit
  19. EP250908C: GROND observation of the fading optical counterpart
  20. GRB 250910A: LCO optical upper limit
  21. EP250908c: SVOM/VT optical observation
  22. EP250908c: VLT/FORS2 optical counterpart identification
  23. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  24. EP250908b: SVOM/VT optical candidate
  25. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  26. GRB 250903A: Swift-XRT afterglow detection
  27. EP250905a: Liverpool Telescope i-band upper limits
  28. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  29. EP250905a: Liverpool Telescope observations
  30. EP250905a: FTW one optical and multiple NIR counterpart candidates
  31. EP250905a: JinShan likely optical counterpart detection
  32. GRB 250905A: Swift/UVOT Upper Limits
  33. GRB250904A: Liverpool Telescope upper limits
  34. GRB 250903A: Swift/UVOT detection
  35. GRB 250905A: KAIT optical upper limit
  36. GRB 250904A: TRT optical counterpart detection
  37. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  38. GRB 250903A: Swift-XRT observations
  39. EP250903a: Swift-XRT observations
  40. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  41. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  42. GRB 250903A: EP-FXT counterpart detection
  43. GRB 250903A: LCO optical observation
  44. GRB 250903A: LCO optical afterglow detection
  45. GRB 250903A: SVOM/VT optical confirmation with VHF data
  46. EP250903a: SVOM/VT optical confirmation
  47. EP250901a: Mondy, Assy and SAO RAS optical limits
  48. Subject GRB 250903A: SVOM/MXT afterglow detection
  49. GRB 250903A: TRT optical counterpart detection
  50. GRB 250903A: SVOM detection of a burst
  51. EP250903a: TRT optical observations
  52. EP 250827B: Detection of supernova counterpart by LCO.
  53. EP/WXT01709201159: GOTO optical follow-up
  54. EP250827b / AT 2025wkm: TRT optical observations
  55. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  56. EP250827b: continued Liverpool Telescope observations
  57. GRB 250902B: SVOM/GRM observation
  58. GRB 250901A: Swift/UVOT Upper Limit
  59. GRB 250902A: SVOM/GRM observation
  60. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  61. GRB 250901A: EP-FXT follow-up observation
  62. GRB 250901A: NOT optical observations
  63. GRB 250901A: SVOM/VT optical afterglow with VHF data
  64. GRB 250901A: LCO optical upper limit
  65. EP250827b: Swift observations of AT 2025wkm
  66. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  67. EP250831a: NOT optical observations and tentative afterglow candidate
  68. EP250827b: FTW Observations of AT 2025wkm
  69. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  70. EP250901a: Mephisto optical upper limits
  71. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. EP250821a: SOAR observations
  73. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  74. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP250828a: Optical counterpart detection with Kinder observations
  76. EP250828a: Liverpool Telescope upper limits
  77. EP-WXT trigger 01709200800 : KAIT optical observations
  78. EP250828a: KAIT optical upper limit
  79. EP250827a: Swift/UVOT Detection
  80. EP250828a: NOT optical counterpart confirmation
  81. EP250828a: SVOM/VT optical candidate
  82. EP250828a: Seimei/TriCCS optical counterpart detection
  83. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  84. EP250828a: Optical upper limit with Kinder observations
  85. EP250827a: LCO observations show fading optical counterpart
  86. EP250827A: VLT/X-shooter redshift confirmation
  87. EP250827a: confirmation of optical rebrightening with LCO
  88. EP250827a: GOTO observation of the optical afterglow
  89. GRB 250826A: SVOM/GRM observation
  90. EP250827A: An optical rebrightening was detected by LCO.
  91. EP250827a: Swift-XRT counterpart detection
  92. EP250827a: TRT optical observations
  93. EP250827a: BOOTES-7 early optical dectection
  94. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  95. EP250827a: Gemini-South redshift z = 1.613
  96. EP250827a: Las Cumbres independent detection of the optical counterpart
  97. EP250827a: Gemini-South optical counterpart detection
  98. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  99. EP250821a: Gemini GMOS Redshift Confirmation
  100. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz

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